PROJECT SUMMARY Vaxiion Therapeutics has developed a novel, non-living oncolytic bacterial minicell-based product candidate, called VAX014. Initially designed for use in the topical intravesical treatment of non-muscle invasive bladder cancer (NMIBC), the IND for this initial indication will soon be open. Data from our recent publication in Nature Molecular Therapy ? Oncolytics demonstrate that VAX014 minicells (published under the research name VAX- IP) selectively kill cancer cells that express unligated cancer associated ?3?1 and ?5?1 integrins via an oncolytic mechanism of action (MoA). These two integrin subtypes are over-expressed in many cancer subtypes and are clinically validated negative prognostic factors for bladder cancer, ovarian cancer, and melanoma. In addition to the direct integrin-targeted tumoricidal effects afforded by VAX014?s oncolytic MoA, VAX014 also exerts indirect synergistic immunotherapeutic effects against tumors, similar to the standard-of-care in NMIBC, intravesicular immunotherapy with live Bacillus Calmette-Guerin (BCG vaccine). Based on all of these factors, VAX014 was evaluated in a pilot study in combination with anti-PD-L1 immune checkpoint blockade using the preclinical syngeneic orthotopic MB49 murine bladder cancer model used to evaluate activity of VAX014 for use in NMIBC. The results of these studies were quite remarkable and despite these animals having large, digitally palpable, ulcerated bladder tumors at the onset of therapy, an overall survival rate of 87.5% was achieved in combination therapy versus 12% and 25% in single agent comparator study arms. Animals that survived combination therapy were rechallenged with a second round of orthotopic MB49 tumors and an impressive 100% of animals rejected tumors and are disease free. These data strongly suggest that the combination of VAX014 and PD-L1/PD-1 blockade results in potent anti-tumor responses made durable by the likely development of long term anti-tumor immunological memory. While marketed immune checkpoint inhibitors against the PD-L1/PD-1 axis result in profound durable clinical responses in some patients, the reality is that they haven?t worked in the majority of patients, including most recently in the JAVELIN-100 study in ovarian cancer. Clinical trials using combinations of T-cell directed inhibitors (e.g. anti-PD-L1 and anti-CTLA-4) have resulted in better response rates, but come at the cost of increased and in some cases, deadly immunotoxicities. This creates a need for better combination partner agents and based on Vaxiion?s preclinical results in combination with anti-PD-L1 therapy to-date, VAX014 may represent an attractive and effective option. For the many reasons described in this proposal, Vaxiion now intends to expand the preclinical evaluation of VAX014 in immune competent mouse models of ovarian cancer and melanoma to study and understand the role of key immune cells behind the immunological MoAs of VAX014 alone and in combination with PD-L1 blockade. Bolstered by big pharma partnering interest, our GMP manufacturing experience and soon-to-be open IND in NMIBC, successful outcome(s) in these important Phase I SBIR studies will enable Vaxiion to springboard VAX014 into the clinic to perform combination therapy trials in these indications.